Effective temperature control



Nov. 5, 1940. e. M. BROWN 2,220,061

EFFECTIVE TEMPERATURE CONTROL Filed Dec. 8, 1937 All/l l/l V INVENTOR91:1 NE Brawn) M 4 ATTORNEY Patented Nov. 5, 1940 UNITED STATES PATENTOFFICE 2,220,061 EFFECTIVE TEMPERATURE CONTROL Guy M. Brown,Minneapolis, Minnf, assignor to Minneapolis-Honeywell Regulator Company,Minneapolis, Minn., a corporation of Minnesota Application December 8,1937, Serial No. 178,732

6 Claims. (Cl. 236-44) stat, and wherein means responsive to the hu-'the temperature should be maintained at a lower' value than is necessarywhen the humidity is low. Many different ways have been proposed to varythe control point of the thermostat in accordance with changes inhumidity, and one effective way is to provide a heater located in heattransfer relationship with the thermostat, the heating effect of theheater varying in accordance with the humidity of the space. By placingthis heater below the thermostat, air will be caused to fiow upwardlyover the thermostat so that the thermostat will respond more quickly tochanges in the space temperature as well as to changes in thetemperature of the heater. It is of importance that. the fiow of airpast the thermostat remain uniform regardless of the heating effect ofthe heater, since if the air were permitted to flow at different rates,the thermostat would not accurately respond to the combined effects ofthe space temperature and the heater temperature, and I have thereforeprovided means to compensate for varying temperatures of the heaterwhereby the flow of air over the thermostat remains substantiallyuniform at all times. This compensating means may be in the form of anadditional heater located above the thermostat at a point where it hasno heating effect on the thermostat but does cooperate with the firstheater in creating the flow of air. amount of air flow depends upon thecombined heating effects of the two heaters, which is main- 45 tainedconstant by increasing or decreasing the temperature of the upper heateras the temperature of the lower heater decreases or increases,respectively.

The controller for the lower heater may be in 50 the form of a humidityresponsive element, which may be located below the thermostat in thepath of the air flow, so that there is a steady flow of air over thehumidity responsive element, but the element is not subjected to theheating 55 effect of the lower heater, whereby this element The quicklyresponds to changes in the humidity in the space being controlled.

It is therefore an object of my invention to provide an improvedcontroller whereby a space may be maintained at a substantially constanteffective temperature.

More specifically, it is an object of my invention to provide athermostat whose control point varies in accordance with the humidity ofa space being controlled, and whereby a uniform flow of air ismaintained over said thermostat at all times.

Other objects will become apparent upon a study of the specification andclaims in conjunction with the accompanying drawing, wherein isillustrated a preferred form of my invention.

Referring more specifically to the drawing, the control means areenclosed by a housing I0, this housing including compartments II and I2separated by a wall |3 which may be of heat insulating material. Athermostat generally designated by the reference character I5 is locatedin the upper part of the compartment II. This thermostat may comprise abimetallic element |6 fixed at one end thereof by means of a bracket I!to a wall of the housing ID, the other end of the bimetallic element Itcarrying a contact l8 and a resilient arm H! which in turn carries asecond contact 20; Fixed contacts 2| and 22 adjustably mounted in posts23 and 24 cooperate with the contacts l9 and 2|], respectively. Thecontacts are so arranged that contact 20 engages contact 22 beforecontact I8 engages contact 2| upon a drop in temperature affecting thethermostat, and upon a rise in temperature contact l8 will disengagecontact 2| before contact 20 disengages contact 22. Heating elements 30and 3| are located below and above the thermostat l3, respectively.Heater 30 will cause a rise in temperature in the thermostat I5 but thetemperature of the thermostat is unaffected by the heater 3|. A thirdheater 32 is also located in heating relationship with the bimetallicelement l6 and is arranged to be heated when the temperature of the airaffecting the thermostat is rising and after the contact |8 has movedaway from contact 2| thus causing the disengagement of contacts 2| and22 more rapidly than would occur in the absence of this heater. Thefunction of these heaters will be more fully set forth later.

Also mounted in the compartment II is a humidity responsive element 35.This element may be composed of hygroscopic hairs 36 or any otherhygroscopic element, these hairs being connected at their upper ends toa bracket 31 suitably connected to a wall of housing ID, the lower endsof the hairs being connected to a member 38 which in turn is connectedby means of a tension spring 39 to the lower wall of the housing l6.Spring 39 acts to move member 38 downwardly upon a rise in humidity inthe air, which rise in humidity causes the hairs 36 to be' elon gated.Upon a drop in humidity, the hairs 36 contract causing member 38 to moveupwardly against the bias of spring 39.

Pivotally mounted in the compartment i2 is a bell crank lever 46, thislever including an arm 4| extending through a slot in wallv l3 andsuitably connected to member 36 of the humidity responsive element 35. Asecond arm 42 of the bell crank lever is arranged to move across apotentiometer resistance 43 upon a movement of arm 4| caused byelongation or contraction of hairs 36 of the humidity responsive element35. An insulated piece 43 may be provided in the arm 42 whereby theupper portion of this arm is insulated from the rest of the bell cranklever. The heat generated by the potentiometer resistance 43 isprevented from afiecting the elements in compartment II by reason of theinsulated 'wall l3. Potentlometer resistance 43 is for the purpose ofvarying the'heating effects of heaters 3| and 32 in accordance with therelative humidity in the space being controlled as will be more fullyset forth in the description of the operation. Apertures 45 and 46 areprovided in the lower and upper walls of the housing l6 for the purposeof permitting an upward flow of air through both compartments of thehousing and over the elements housed therein.

Lines 56 and 5| are provided for conveying current from ,a suitablesource of power (not shown) to the various parts of my system. Connectedby means of conductors 52 and 53 is a primary 54 of a step-downtransformer, this transformer also including a core 55 and a 590-,ondary 56. A relay generally designated by the reference character 66 isprovided and includes a relay coil 6|, an armature 62, switch arms 63and 64, and contacts 65, 66, and 61. Switch arms 63 and 64 are arrangedto engage contacts 65 and 66 upon energization of the coil 6|, and upondeenergization of the coil 6|, the arms move out of engagement withcontacts 65 and 66 and arm 64 moves into engagement with contact 61. Thelow tension secondary 56 of the transformer supplies power for therelay-coil 6| and also for the heaters 36, 3|, and 32.

Suitable heating and cooling apparatus may be connected to the lines 56and 5| and are controlled by the switch arm 64 of relay 66. The heatingapparatus may be connected to the lines 56 and 5| when the switch arm 64is in engagement with contact 66 through the following circuit: from theline 5| through conductor 16, switch arm 64, contact 66, conductor 1| tothe apparatus and back through conductor 12 to the line 56. When the arm64 is in engagement with contact 61 for cooling apparatus may be.connected to the lines through conductor 16 fr om line 5|, switch arm64, contact 61, conductor 13 through the cooling apparatus and backthrough conductor 12 to the line 56; Since the heating and coolingapparatus form no part of my invention they have not been illustrated.It should be understood that during the heating season the coolingsystem may be rendered inoperative by operation of a manual switch sothat engagement of switch arm 64 with contact 61 will not causeoperation of the cooling system and likewise during the cooling season,the heating system may be rendered inoperative by any suitable switchmeans.

Operation in the operation of the system the relay 66 is under thecontrol of the thermostat |5. When the temperature in the air passingover the thermostat I5 drops to a suificiently low value, contacts l6and 26 will engage contacts 2| and 22, respectively, and cause theenergization of relay coil 6| by means of the following circuit: fromthe transformer secondary 56 through conductors 15. 16, 11, fixedcontact 22, contact 26, arm l9, bimetallic element l6, contacts l6 and2|, conductors 18, 19 through the relay coil 6| and conductor 86 to theother side of secondary 56. Energization of coil 6| causes arms 63 and64 to move into engagement with contacts 65 a'nd66, respectively.Engagement of arm 64 with contact 66 will cause the operation of theheating means, it being assumed for the present that the system isoperating during the heating season. Engagement of arm 63 with contact65 creates a holding circuit for the relay coil 6|, which circuit isindependent of contacts I8 and 2| so that coil 6| will remain energizeduntil contact 26 is moved away from contact 22, this holding circuitbeing as follows: from the secondary 56 through conductors 15, 16, 11,contacts 22 and 26, arm l9, bimetallic element l6, bracket l1, heater32, conductor 82, arm 63, contact 65, conductors 83 and 19, coil 6| andconductor 86 to the other side of the secondary 56. It will be notedthat this holding circuit for the relay 66 includes the heater 32 sothat upon the disengagement of contacts 8 and 2|, which occurs after thetemperature has risen to a predetermined degree, heater 32 begins toheat up so that the thermostat becomes heated thereby iaster than it isheated by the air passing thereover and contact 26 moves away fromcontact 22 sooner than it would were the heater not present. Byaccelerating the opening of..contacts 26 and 22 and the deenergizationof the relay 66 the heating system is stopped sooner than it otherwisewould be and the inherent lag of the heating system is therebycompensated for. In other words, the danger of the temperatureover-running by reason of the lag in the heating system is considerablyreduced by reason of the heater 32.

Heater element 36 is at all times energized by the following circuit:from the transformer secondary 56 through conductors 15, 96, heater 36,conductor 9| through the portion of the potentioineter resistance 43 tothe left of arm 42, through arm 42 and conductor 92 to the other sideofsecondary 56. The heater 3| is also continuously energized by thefollowing circuit: from transformer secondary 56 through conductors 15,16, 94, heater 3|, conductor 95 through the portion of potentiometerresistance 43 to the right of arm 42, through arm 42 and conductor 92 tothe other side of secondary 56. It will be apparent that the amount ofcurrent through heaters 36 and 3| depends upon the position of arm 42with respect to resistance 43. Thus, if the arm 42 moves toward the leftthe amount of resistance in series with heater 36 is reduced and theamount of resistance in series with heater 3| is increased, whereby theheating efiect of heater 36 increases and the heating efiect of heater3| decreases. Upon movement of arm 42 to the right, the opposite effectresults. Heaters 30 and 3| are preferably of substantially the samecapacity so that the combined heating effect of the two heaters willremain substantially constant regardless of the position of arm 42 withrespect to resistance 43.

Resistance 30 being located below the thermostat l causes the thermostatto respond to a temperature which is higher than the temperature in thespace being controlled and the difference in the temperature of the airaffecting the thermostat and the temperature of the air in the space iscontrolled by the heating effect of heater 30; Movement of arm 42 iscontrolled by the humidity responsive element 35 and accordingly theheating effect of heater 30 is under the direct control of thehumidityresponsive element 35, or in other words, the humidity of thespace being heated. Upon an increase in the humidity of the space forexample, member 38 moves downwardly, thus permitting downward movementof arm 4! under the bias of spring 39 which causes movement of arm 42 tothe left over resistance 43. This in turn causes an increase in heatingefiect of heater 30 so that the thermostat is heated to a higher valueby this heater with the result that a lower temperature is maintained by.the thermostat in the space being heated. On

the other hand as the humidity in the space decreases, arm 42 is causedto move to the right over resistance 43 thus decreasing the effect of.heater 30 so that a higher space temperature is required to satisfy thethermostat I5. It will thus be seen that by properly proportioning thevarious parts the effective temperature in the space may be maintainedat a substantially constant value.

Air is caused to circulate upwardly through openings 45 over thehumidity responsive element 35 and the thermostat l5 by means of heaters30 and 3|. By maintaining a steady flow of air from the space over theseelements it will be obvious these elements will more quickly respond tochanges in the humidity or the temperature in the space beingcontrolled. It is of importance however that this flow of air bemaintained uniform for varying conditions as a varying flow of air wouldvary the responsiveness of the thermostat [5. By reason of the heater 3|cooperating with the heater 30, as previously described, this flow ofair maybe maintained at a substantially uniform value regardless of theheating effect of heater 30 on the thermostat l5. By locating thehumidity responsive element 35 below heater 30, the temperature of theair as it passes over this element will be the same as the temperatureof the space and consequently this element will correctly respond tovarying changes in the relative humidity in the space. Theprovision ofthe wall l3 of insulating material separating the resistance 43 andtheelements in compartment ll insures that the temperature of thisresistance will have no effect upon the elements in the compartment l I.

During the cooling season the operation will be substantially the sameas that above described except that the cooling system will be placed inoperation whenever arm 64 engages the contact 61 which occurs wheneverthe relay is deenergized. When the effective temperature in the spacedrops to a low enough value and contacts l8 and 20 engage contacts 2|and 22, respectively, of the thermostat IS, the relay 6| will beenergized and arm 64 will move away from contact 61, thus interruptingthe operation of the cooling system. The efl'ect of heater 30 will bethe same as during the heating cycle, cooperating with the thermostat I5to vary the temperature in the space according to changes in thehumidity existing therein. The operation of the system during thecooling season should be readily understood by those skilled in the artupon a study of the description of the operation of the system duringthe heating cycle, and a further description is believed unnecessary.

It will thus be seen that I have provided a controller by means of whichthe temperature of a space may be maintained at a constant effectivevalue during either the cooling or the heating seasons, the controllerbeing compact and one which will very quickly respond to changes in thetemperature or humidity of the space being controlled.

Having described a preferred form of my invention, many modificationsmay become apparent to those skilled in the art and it should beunderstood that the invention'is to be limited only by the scope of theappended claims.

I claim as my invention:

1. An effective temperature controller comprising a temperatureresponsive element, a heater located below said temperature responsiveelement for raising the temperature of said element above thetemperature of a space being controlled, a second heater located abovesaid temperature responsive element, and cooperating with said firstheater to cause a flow of air over said heater and said temperatureresponsive element, condition responsive means for controlling theheating effect of the first heater and for simultaneously controllingthe heating efiect of the second heater whereby the combined heatingeffect of the two heaters remains constant at all times, therebyinsuring that the fiow of air over said thermostat'will remain constantregardless of the heating effect of the first heater.

2. An effective temperature controller comprising a temperatureresponsive element, casing means surrounding said element and providingfor a flow of air vertically upward over said element, heating meansbelow said element in the path of air flow, heating means above saidelement in the path of air flow, and means for increasing or decreasingthe heating effect of said first heating means as the relative humidityin the space whose temperature is being controlled increases ordecreases and simultaneously decreasing or increasing the heating effectof the second heating means whereby the two heating means cooperate tocause a uniform flow of air over the first heating means and thetemperature responsive element regardless of the heating effect of saidfirst heating means.

3. An effective temperature controller comprising a temperatureresponsive device, a housing surrounding said temperature responsivedevice having air inlet and outlet openings at the bottom and toprespectively, a heater located in heat transfer relationship below saidtemperature re-" sponsive device, means for varying the heating effect'of said heater in response to changes in humidity in a space whosetemperature is being controlled, and means cooperating with said heaterto at all times maintain a uniform flow of air over said temperatureresponsive device regardless of the heating effect of said heater.

4. An efiective temperature controller comprising a temperatureresponsive device, a humidity responsive device, a housing surroundingsaid devices with the temperature responsive device in the upper portionthereof and the humidity responsive device in the lower portion thereof,said housing having air inlet and outlet openings in the bottom and toprespectively, a heater located in heat transfer relationship with saidtemperature responsive device near the lower portion thereof and abovesaid humidity responsive device, means under the control of saidhumidity responsive device for controlling the heattemperatureresponsive device near the lower portion thereof and above said humidityresponsive device, means under the control of said humidity responsivedevice for controlling the heating efiect of said heater, a heaterlocated above said temperature responsive device, and means,

for at all times maintaining the combined heating effect of the twoheaters constant, whereby a constant flow of air is created by theheaters over the first heater and the temperature responsive deviceregardless of the heating efiect of the first heater.

6. An eflective temperature controller comprising in combination, atemperature responsive element, heating means in heat exchangerelationship with said element, humidity responsive means varying theamount of heat given off by said heating means in accordance withvariations in humidity, said heating means inducing a flow of air pastsaid element which varies in accordance with the amount of heat givenoff by said heating means, and means acting in conjunction with saidheating means to maintain a constant flow of air past said elementregardless of the amount of heat given 01? by said heating means.

GUY M. BROWN.

